Description ALL BIRDS (ages are not separable in the field) Have dark grayish brown upper wing coverts and mantle, contrasting with darker wingtips. Note the darker tail and contrasting white upper tail coverts. Dark cap is separated from mantle by incomplete white collar. Underparts are mainly white with dark markings.

Dimensions Length: 18-20" (46-51 cm)

Habitat Breeds on South Atlantic islands (in our winter) and undertakes circum-Atlantic nonbreeding travels; present in North Atlantic in summer months and commonest Jul-Sep. Numbers vary from year to year but usually common in offshore waters.

Observation Tips Only very occasionally comes close enough to shore to be seen from land but easy to see on pelagic and whale-watching trips, typically well out of sight of land.

Discussion Similar to Cory's but separable by plumage differences, and because generally it flies on stiffer wings. Effortless flight is masterful in strong winds. Sometimes gathers in large flocks in areas of good feeding (e.g. where fish are shoaling, or around fishing boats). Sexes are similar.